Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

Walk behind a 50-meter-high waterfall.

Walk 2,300 feet above the ground on the "Troll's Tongue."

Monuments don't get much more metal than these three giant viking swords planted in a Nordic hill.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.

This outdoor gallery of sculptures along the East River was once a landfill.

Little Red Lighthouse under the George Washington Bridge.

This futuristic airport terminal was abandoned for decades before reopening as a hotel—with a vintage plane of its own parked out back.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Lie in a hammock where George Washington stood.

Try not to get slimed in Tribeca.

There must be a pun in this haystack somewhere...

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

Why walk on this historical site when you can zoom down instead?

One Portuguese poet described this cape, the westernmost point in mainland Europe, as "where the land ends and the sea begins."

In Portugal, a secluded stretch of untouched natural beauty hides at the bottom of a steep hill.

At night, bats patrol this magnificent 18th-century space in search of book-eating pests.

This is not only one of the oldest collections in Europe, but also possibly the most beautiful.

Roman ruins top white travertine terraces formed by ancient hot springs.

The patron of this extravagant Art Nouveau confection insisted that nothing less than a boat should project from its facade.

This home on a quiet suburban street is completely covered with vibrant mosaics.

Artists and musicians now rule over this former rail station.